1. Field of the Invention
The present invention relates to an acid generating agent, and more particularly, to a salt suitable as an acid generating agent used in chemically amplified resist compositions that are used in semiconductor processes.
2. Description of the Related Art
A chemically amplified resist composition used in the semiconductor fine processing utilizing lithography contains an acid generating agent, and as the technologies supporting the semiconductor fine processing continue to develop, a demand for resists with higher resolution still exists.
Therefore, in order to produce a resist having an increased resolution and desired properties, a large number of different acid generating agents have been developed.
Development of photo-acid generating agents for chemically amplified resists has been carried out such that low sensitivity ionic photo-acid generating agents such as iodonium salts were initially used, and at the same time, non-ionic photo-acid generating agents were developed, so that such an agent would generate a sulfonic acid derivative such as toluenesulfonic acid, when irradiated with light, and induce a deprotection reaction for resins. Thereafter, the tendency has been such that more derivatives of sulfonyl salts having faster response time are produced, and modification is more weighted on the cation part, thus resulting in a variety of sulfonyl salts.
According to the recent trend in the development of finely patterned resists requesting even smaller line widths, the line edge roughness of resist has been the most urgent problem to be addressed. Furthermore, there is rising another problem of reducing the amount of the salt of a photo-acid generating agent eluted into water, as water is used in the processes of argon fluoride (ArF) immersion lithography. In an attempt to improve the circumstances, the development of photo-acid generating agents began to involve modification of the anion part, in view of improving the diffusion rate of acid and transparency, and reducing the elution of the photo-acid generating agent into water. Furthermore, new inventions focused on the anion moiety of acid generating agents have recently been achieved, on the bases of numerous experimental results and reports showing that the anion moiety has substantially greater influence than the cation moiety on the physical and chemical characteristics which can improve the fluidity of acid and the properties of the resist composition. Thus, the trend of the development is now focused on photo-acid generating agents that are capable of reducing the diffusion rate of acid, and have good transmissibility of ArF laser at 193 nm.
Therefore, attempts are rapidly being made to introduce a bulky alicyclic ring, or an alkyl group, alkoxy group or ether group having a large number of carbon atoms into a salt suitable as a photo-acid generating agent (see Korean Patent Application No. 10-2006-0114104, 10-2007-0069049, 10-2005-0107599 and 10-2007-0053619).